Neural circuitry: latent, passive, and active acupoints

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To continue the series of posts based on quotes from the text Biomedical Acupuncture for Pain Management, let us discuss the concept of qualifying acupuncture points as “latent”, “passive”, or “active”.

Latent points are those which are not at all tender to a patient (normal tissue state), passive points are those that when palpated with some pressure are found to be tender, and active points are those that are tender even without any stimulation.

Considering the neurogenic nature of acupoints, we can consider chronic pain to be a condition in which many acupoints are classified as “active”.

…acupuncture needling increases impulses from passive acupoints but calms signals from active acupoints. This electrophysiologic difference between passive and active acupoints has been confirmed by experimental data in rats (Y.-T. Ma, unpublished data).

Ma, S., & Sun, S. (2014). Biomedical Acupuncture for Pain Management: An Integrative Approach. Elsevier.

This increase or decrease in firing rate due to acupoint state when needled is extremely interesting considering recent work on Spike timing dependent plasticity, and neural plasticity generally.

When presynaptic activity precedes postsynaptic activity with a certain temporal delay, it can lead to a strengthening of the synaptic connection. This phenomenon is known as spike-timing-dependent plasticity (STDP). On the other hand, if the postsynaptic activity precedes the presynaptic activity, the synaptic connection may be weakened or depressed.

The underlying mechanism of time-dependent reinforcement involves the coordination of synaptic input and postsynaptic firing, which can lead to long-term changes in synaptic strength and contribute to learning and memory processes. By integrating information from multiple neurons over time, the brain can modify the strength of connections based on the temporal relationship of neural activity.

Research on acupuncture and neural plasticity has gained significant attention in recent years. Several studies have explored the effects of acupuncture on various aspects of neural plasticity, including synaptic plasticity, cortical remapping, and neuroplastic changes in pain processing.

One area of interest is the modulation of neurotransmitters and neurotrophic factors by acupuncture. Studies have shown that acupuncture can influence the release of neurotransmitters such as endorphins, serotonin, and dopamine, which can have modulatory effects on neural plasticity processes. Acupuncture has also been found to promote the expression of neurotrophic factors like brain-derived neurotrophic factor (BDNF), which plays a crucial role in synaptic plasticity and neuronal survival.

In terms of cortical remapping, research has demonstrated that acupuncture stimulation can lead to changes in the somatosensory cortex representation of specific body regions. These changes are thought to reflect neuroplastic adaptations in response to the sensory input generated by acupuncture.

Furthermore, acupuncture has been studied for its effects on pain processing and chronic pain conditions. It has been suggested that acupuncture can induce neuroplastic changes in the central nervous system, including the modulation of pain-related brain regions, alteration of pain signaling pathways, and the activation of endogenous pain inhibitory systems.

By MEpps

Offering acupuncture, massage, and herbal medicine at the L'Etoile, espace thérapeutique since 2004.